Wizbanga*

Hey, I'm having a few probs with my S5 sev, any help would be appreciate

6 weeks ago I was heading to the drags when I lost my rev counter on the way up, didn't think this was to much of a prob, but a few days later it went BANG, the oxygen sensor came flying out the exhaust, so I put anew one in it hoping that would fix the problem but it hasn't.

I can get it to idle, but as soon as any load is put on it backfires and when it reaches about 4000rpm it back fires. We have replaced the computer, crank angle sensor, TPS sensor, leads, coils, spark plugs, and done a compression test, and nothing has worked the compression is sweet. Also the trailing coil is firing when you crank it but not when it reaches that 4000rpm, is osmething possibily telling it not to fire, it does not appear to be faulty.

Wat else could be wrong, please help as I want my baby back!!!!!!

SureShot

You have done it all already (coils, leads, plugs).

But wait - how about a nice heavy ground from the block to the coil mounts?
Yea - that should do it..

skyypilot

Yea, try adding grounds, the standard set, several good threads on this

Cory Simpson

I put grounds on my car and I think it made it start running worse, I'm not sure why.

jon88se

bc now that the car has decent grounds some problems may be magnified. Check TPS, Timing and vacuum leaks

Black13B

iTrader: (1)

if your car ran worse after grounds, your car has some major voltage issues

you sure you properly installed decent grounds?

grounds ONLY help - and uncovering voltage issues is still a big help..

imagine how bad it could get if you just let it keep going with the bad grounds and bad volts..

SureShot

Here is why:
The ECU uses low voltage signals from sensors (like the TPS) to controls (like the BAC).
Most of these sensors have their own ground wires, but if the primary grounds are the least bit weak, the sensor grounds try to carry the noisy spark and alternator loads also.
The ECU tries to compensate for the extra switching loads & goes nuts.
Then you go nuts.

Nick86

iTrader: (1)

Check your Air Flow Meter. Make sure it is working properly. I believe that there are tests you can do. Check a Haynes or Factory Shop Manual. (SureShot has a link to the FSM above ^)

You should also inspect the O2 sensor wire. If it touched the hot exhaust when the previous one went bang, the wire might be shorting out and sending "Limp Mode" signals or something.

When was your last fuel filter change?

MasteRX

I dont think anyone has mentioned this, but I believe you should add a good ground wire. I had a problem where my tach went out as well, it turned out to be bad grounding. My theory is that the root of the bad grounding problem is when people put on aftermarket exhaust and get rid of that ground strap that is on the stock exhaust. This overloads the small ground wire from the block to the firewall and then causes electrical problems. Check this wire (it is about a 10 guage wire, it plugs into a connector on the firewall) and see if it looks melted or anything. On my car I just replaced this wire with some 4 guage and problems solved. I was also thinking about adding a new ground strap to my current exhaust for good measure.

SureShot

Where have you been?

I know - you have patterned yourself by scrolling to the bottom of EULA's without reading.

(I rarely flame - but...)

MasteRX

It was a joke.

I really just wanted to put my aftermarket exhaust theory out there.

SureShot

MasteRX - You better duck as we all throw our pre-cats at you.

Pretty soon it will be Wed AM in NZ and Wizbanga* is going to see all this crap in her thread.

Wizbanga*

Thanks guys, I'll see what happens

Cory Simpson